The present invention relates generally to metallocarborane compounds which are useful as hydrogenation, hydroformylation and isomerization catalysts. More particularly, the present invention relates to the discovery of an extraordinarily active metallocarborane catalyst.
In recent years, the discovery and utility of homogenous and heterogenous hydrogenation, hydroformylation and isomerization catalysts have expanded in scope to become one of the largest areas of endeavor in organic chemistry. Among the more promising catalysts are those catalysts based on metallocarborane compounds. In U.S. Pat. No. 3,976,596, issued to Hawthorne et al. on Aug. 24, 1976, the discovery of a family of stable metallocarboranes based on rhodium and iridium were first described as being effective catalysts for the homogenous hydrogenation, isomerization and hydroformylation of olefins and the hydrosilation of ketones. The metallocarborane catalyst disclosed in U.S. Pat. No. 3,976,596 includes a metal such as rhodium or iridium symmetrically bonded to the pentagonal face of a dicarbollide ligand. The compound further contains two triphenylphosphine ligands and one hydrogen ligand bound to the metal at the remaining ligand sites. This particular type of metallocarborane catalyst has been found to be relatively reactive when used as a homogenous catalyst.
U.S. Pat. No. 4,062,883 issued to Hawthorne et al. on Dec. 13, 1977 discloses a heterogeneous metallocarborane catalyst based on their original metallocarborane which is bound to a polymer support by a carbon-boron bond. By attaching a polymeric support to the carborane cage or dicarbollide ligand, this second patent issued to Hawthorne et al. discloses the conversion of the original homogeneous metallocarborane catalyst into a heterogeneous catalyst which could be more easily removed from solution.
Although both of the above-discussed metallocarborane catalysts are satisfactory it would be very desirable if there could be developed metallocarborane catalysts which are even more highly reactive.